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Vintage threads from the first ten years

Trem question

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7/7/1999 10:38 PM
Niek	Trem question Hi there, Can somebody tell me what the amplitude of the tremolo waveform is on fender amps ?? What does the waveform look like ? I reckon it's sort of sinusoidal. Need this info for a tube reverb/tremolo unit I'm designing. Thanks a lot, Niek

7/9/1999 4:08 AM
moocow	Which one are you interested in ? I can think of four different Fender tremolo circuits. Some work better with low-level signals than others. Also, the modulation envelope varies depending on the circuit. You might want to look at this to get yourself started: http://www.patents.ibm.com/cgi-bin/viewpat.cmd/US05333203__

7/9/1999 3:41 PM
Niek	Thanks a lot Moocow, This is good stuff. I'll work it through and might get back to you with a few questions. I don't want to use an optoisolator in my unit though, I want to apply the trem output signal to the grid for bias modulation (a la Matchless vibrobox & Fender harmonic trem). Cheers, Niek

7/10/1999 10:43 PM

The signal is usualy a sign wave.

the Fender harmonic tremolo doesn't work on the bias of the power tubes. it's way more complicated.

If you want the tremolo working on the grid bias check out the Fender tweed and brown Vibrolux/Tremolux circuit. it's very unclomplicated and works like a charm. Also sounds much better than the opto circuits.

For a much better sounding trem look at a Supro S6622 (tremoverb) schematic, a little more involved but sounds great.

the Vibro Champ circuit is ok but doesn't work well in high gain amps.

Keith

7/11/1999 11:33 AM

Thanks Keith,

Yeah, I know about the harmonic trem, oscillator into phase splitter and highs & lows get modulated by a 180 degrees out of phase oscillator signal. Must sound really cool. I am thinking about building this circuit at a later stage using solid state for the oscillator and splitter and a valve for the hi/lo amplifier stage.

Do you have a copy of that supro schematic you could email me ?

Cheers,

Niek

7/11/1999 6:02 PM
Niek	Sorry, just found the schematic here: ftp://schematics:schematics@24.114.14.68/supro/S6622.jpg There's more stuff as well. Niek

7/12/1999 4:02 PM

Do you happen to have one of these amps, or have you built one? I was wondering what the reverb sounded like. Have you heard one of these amps, or did you build the trem circuit into something else?

Ever since I saw the schematic for the S6622 amp in Weber's "Hip Vintage Guitar Amps" book, it seemed like an interesting amp for recording. It's got tremelo, reverb, but is a single ended 6V6 with a 5Y3 rectifier. The factory version was built with a 10" speaker, but I was going to try it with a 12" alnico for a little more bottom. You'll note that there's an interesting (not usually seen in guitar amps) high pass filter network ahead of the volume control, I guess to limit drawing useless bass frequency energy that the 10" speaker couldn't produce sonically.

Thanks for the schematics bookmark.

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